What recourses do I have to prompt delinquent repayment from a developer who accepted 401k funds?

I utilized a self-directed investment tool through a Bank and Trust to invest my SEP-IRA funds in a land/building development. The terms were for 18month to acquire an old parcel of land and then to sell that land to the bigger project. The land and subsequent sale were completed two years ago but the terms of the original investment allowed the money to stay invested for the same growth rate; to be called due by me at any time. Six months ago I called it due but the developer has dodged his commitment and repaid none of the investment. This raises two questions: 1. What is the standard recourse for me to recover my principal and pledged interest? 2. Does the fact that the Developer accepted IRA funds and the rules attached bring into play any regulatory agencies, like the SEC, for added leverage toward completing the terms of the Agreement?